In a wireless system in which data is transmitted in the unit of superframe, the uplink/downlink of wireless air interface transmission transmits data generally in the unit of superframe; wherein each superframe is composed of one preamble and several PHY Frames (physical frames); in addition, both the preamble and the PHY Frame are composed by taking orthogonal frequency division multiplexing (OFDM) symbol as the basic unit.
The present ultra mobile broadband (UMB), long-term evolution (LTE), worldwide interoperability for microwave access (Wimax) system all have two duplex modes: the frequency division duplex (FDD) mode and the TDD mode.
In the FDD mode, the uplink/downlink uses different frequency band to transmit data; in this way, the resource allocations of uplink/downlink PHY Frames in the system are relatively independent, i.e., the resource allocation may be respectively performed to the downlink PHY Frames and the uplink PHY Frames.
In the TDD mode, since the uplink/downlink performs time division transmission in the same frequency band, the system may divide the PHY Frames into uplink physical frames and downlink physical frames based on a certain proportion according to the requirement of service. However, if the ratios of the numbers of the uplink/downlink PHY Frames of adjacent cells in the same frequency band are different, or the superframes of adjacent cells in the same frequency band do not align to each other, interference between adjacent cells will occur, and there exists also difficulty in networking.